A turbocharger may compress air supplied to an engine to improve engine performance. Speed of a turbocharger may be controlled via a waste gate. The waste gate may be selectively opened and closed to regulate compressor speed. Nevertheless, a turbocharger compressor may be prone to oscillate if a large change in flow through the compressor occurs. For example, a compressor may begin to oscillate if a driver at least partially releases an accelerator pedal from a higher driver demand to a lower driver demand. Quickly closing the throttle may cause air flowing through the compressor to decrease so that the compressor begins to oscillate. One way to reduce the possibility of compressor oscillation is to install a compressor bypass valve that allows air to return to the compressor's inlet from the compressor's outlet. However, the energy applied to pressurize the air is lost and not recoverable when the compressor bypass valve is opened. Further, if the driver applies the accelerator pedal after air pressure downstream of the compressor is reduced; the turbocharger may not be able to provide a desired engine air flow. Consequently, the driver may experience “turbocharger lag” (e.g., a delay in engine torque production due at least in part to air flow through the turbocharger being lower than is desired) until air flow through the turbocharger is sufficient to provide the desired engine air flow. Therefore, it may be desirable to provide a way of reducing compressor oscillation while not releasing boost or contributing to the possibility of turbocharger lag.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method for operating engine compressors, comprising: receiving sensor data to a controller; and activating a second compressor in an engine intake via the controller in response to a first compressor being within a threshold air flow of a surge condition based on the sensor data.
By activating a second compressor in an engine air inlet passage, it may be possible to provide the technical result of adjusting air pressure in the engine air inlet upstream of the first compressor so that the possibility of speed oscillations of the first compressor may be reduced. In one example, air flow through the second compressor is adjusted to decrease pressure at an outlet of the second compressor in response to a pressure increase at an outlet of the first compressor. In this way, boost produced by the first compressor may be conserved so that if a driver increases a demand torque, air may be available to increase engine power with little or no turbocharger lag.
The present description may provide several advantages. For example, the approach may conserve boost provided by a turbocharger. Further, the approach may improve engine air fuel control via reducing pressure oscillations in the engine intake passage. Further still, the approach may provide quick access to boost pressure after a driver reduces a driver demand torque.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.